In particular, the invention relates to a hinge-lid type cigarette packet of the type comprising a cupped container that presents a front face and a rear face, mutually opposed and parallel, two flank faces disposed mutually parallel and perpendicular to the front and rear faces, a bottom end face perpendicular to the front, rear and flank faces, and an open top end. The packet also comprises a lid, likewise of cupped embodiment, hinged to the container along an edge of the aforementioned rear face that coincides with a top edge of the open end. The lid is rotatable thus about the hinge toward and away from a position in which the open top end of the container is concealed, and presents a front face and a rear face, mutually opposed and parallel, two flank faces mutually parallel and perpendicular to the front and rear faces, also a face disposed perpendicular to the front, rear and flank faces and constituting the top end face of the packet.
The packet also comprises a stiffening frame bent to assume a U profile, located internally of the container in part and disposed in contact with the inside of the front face and the flank faces of the selfsame container, which presents a breast piece, and two side pieces joined to the breast piece along respective corner edges. Both the breast piece and the side pieces project upward from the open top end of the container to engage the lid in part.
The main function of the frame in rigid packets of the type described above, generally considered, is to ensure a degree of interference with the lid such as will reduce the likelihood of the selfsame lid being opened accidentally.
In order to maximize this interference and thus maintain the hinged lid as stably as possible in the closed position, the prior art embraces the expedient of cutting C-shaped slits in the corner edges of the frame, each generating a respective tab that projects toward and engages the inside of the relative flank face of the lid when the lid occupies the closed position, thereby increasing the degree of interference.
This method of retaining the hinged lid in the closed position has been found effective enough in the case of conventional rigid packets typified by a parallelepiped geometry with sharp longitudinal corner edges, but has proved ineffectual in the case of packets designed for example with rounded or bevelled longitudinal corner edges, that is to say, all those styles of packets in which the tabs generated by the C-slits are unable, by reason of the particular shape selected for the packet, to interfere with the flank faces of the lid in such a way as will retain it stably and correctly in the closed position.
The object of the present invention is to provide a rigid packet with a hinged lid that is unaffected by the aforementioned drawbacks.